The process as described in the aforementioned U.S. Pat. No. 3,966,459, is directed to a vacuum dissociation of a pelletized molybdenite concentrated feed material at an elevated temperature, producing pellets of relatively pure metallic molybdenum and the process as described in the aforementioned copending continuation-in-part application is directed to the further embodiment of producing ferromolybdenum alloys containing controlled amounts of iron and molybdenum by the vacuum smelting of a pelletized mixture comprised of a molybdenite concentrate and an iron-bearing material at an elevated temperature, producing ferromolybdenum alloy pellets which are eminently suitable for use as an alloying addition agent in steel-making operations and the like. The present continuation-in-part application is directed to still another embodiment of producing ferrotungsten alloys containing controlled amounts of iron and tungsten, which also are suitable for use as an alloying addition agent in iron and steelmaking operations.
Ferrotungsten alloys are produced in accordance with prior art practices by either employing a thermite process or an electric furnace reduction process. Both of these techniques require substantial amounts of labor and energy and are, therefore, somewhat costly. In the thermite process, for example, a tungstic oxide feed material derived from a chemical pretreatment of a tungsten ore concentrate is mixed with reducing agents, such as silicon and/or aluminum, which through an exothermic thermite-type reaction, produces an ingot or button of the ferro-alloy. The ferro-alloy button usually is of a segregated structure and further requires crushing and sizing prior to shipment and use. The slag produced, for economic reasons, is usually subjected to further treatment for recovery of residual metal values and the treated residue is discarded. In addition to the relatively high costs of the reducing agents required in the thermite process, further problems are presented from an environmental standpoint as a result of the disposal of the slag produced and the treatment required of the gases evolved during the exothermic reaction.
The present process overcomes many of the problems and disadvantages associated with prior art techniques for producing ferrotungsten alloys by utilizing a tungsten ore concentrate directly as the starting material without requiring costly chemical pretreatments to extract the tungstic oxide. Carbon is employed as a low-cost reducing agent, eliminating the formation of any slag, whereby a ferrotungsten alloy is obtained which is of a nonsegregated structure and is in the form of pellets, avoiding the necessity of subjecting the ferro-alloy to a crushing operation as in the case of buttons produced by the thermite process.